A standard power brush has as disclosed in U.S. Pat. No. 5,524,315 an arbor that extends along an axis and that is rotated at high speed about the axis. A brush has a sleeve fitted to the arbor and a multiplicity of bristles that extend radially outward from the arbor. In use the brush is rotated at high speed while outer ends or tips of the bristles are pressed against a workpiece so as to strip paint, descale, deflash, roughen, or otherwise surface treat the workpiece. The bristles can be made of natural or synthetic fibers, or of metal. They are at least limitedly flexible and can be formed as wires, strands, or flat sheets extending generally in planes radially from the axis.
In commonly owned US 2005/0241085 a dressing device for provided for a power brush having a housing, a brush rotatable on the housing about a brush axis and having bristles extending generally radially of the axis, and a drive that rotates the brush in a working direction about the axis and thereby orbits tips of the bristles about the axis so in use the brush is rotated in this working direction. In this apparatus a support immediately adjacent the housing carries a rigid grinding wheel having an abrasive outer surface. This wheel is biased radially against the bristle tips to sharpen and clean them while a drive relatively displaces the bristle tips and the grinding-wheel surface while the wheel is urged against the bristle tips such that the grinding wheel surface primarily engages rear sides of the bristle tips turned away from the working direction. The wheel is provided upstream in the rotation direction of the from the region where the bristles contact the workpiece, typically offset by about 90° or more upstream. A similar system is shown in JP 2001334453 of Ono Shusuke.
The known brush assemblies have generally proved themselves, but are limited in case of treatment depths of 50 μm, 60 μm, but rarely more than 70 μm. To date such treatment depths can generally only be achieved by sand blasting. In fact, such treatment depths are required for preparing a workpiece surface for example prior to a coating process for subsequently assuring firm adherence of a coating. The described sand blasting however is limited due to environmental reasons, since the particles of the material that is separated from the workpiece gets mixed with the sand being used and formed with it hazardous waste requiring special disposal/treatment procedures. Moreover, sand blasting requires expensive machinery and additional safety measures for protecting adjacent surfaces that do not need to be abraded. This is time-consuming as well as expensive.